Updates with pricing details

** American Superconductor's AMSC.O shares down 17.3% premarket at $28.50 after equity raise

** Ayer, Massachusetts-based power grid systems and solutions provider says sold ~4.1 mln shares at $28 for gross proceeds for $115.5 mln

** Offering price is 18.7% discount to stock's last close on Tues

** Co plans to use net proceeds for working capital and general purposes, including potential acquisitions

** Oppenheimer sole bookrunner for offering

** With ~39.5 mln shares outstanding, co has roughly $1.4 bln market cap

** AMSC shares on Tues closed up 4.1% at $34.45, up 40% YTD

** All 3 analysts covering AMSC are bullish with $39 median PT, LSEG data reflects

(Lance Tupper is a Reuters market analyst. The views expressed are his own)

((lance.tupper@tr.com 1-646-279-6380))